1 /*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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24
25 #ifndef SHARE_VM_MEMORY_SPACE_INLINE_HPP
26 #define SHARE_VM_MEMORY_SPACE_INLINE_HPP
27
28 #include "gc_implementation/shared/liveRange.hpp"
29 #include "gc_implementation/shared/markSweep.inline.hpp"
30 #include "gc_implementation/shared/spaceDecorator.hpp"
31 #include "gc_interface/collectedHeap.hpp"
32 #include "memory/space.hpp"
33 #include "memory/universe.hpp"
34 #include "runtime/prefetch.inline.hpp"
35 #include "runtime/safepoint.hpp"
36
37 inline HeapWord* Space::block_start(const void* p) {
38 return block_start_const(p);
39 }
40
41 inline HeapWord* OffsetTableContigSpace::allocate(size_t size) {
42 HeapWord* res = ContiguousSpace::allocate(size);
43 if (res != NULL) {
44 _offsets.alloc_block(res, size);
45 }
46 return res;
47 }
48
49 // Because of the requirement of keeping "_offsets" up to date with the
50 // allocations, we sequentialize these with a lock. Therefore, best if
51 // this is used for larger LAB allocations only.
52 inline HeapWord* OffsetTableContigSpace::par_allocate(size_t size) {
53 MutexLocker x(&_par_alloc_lock);
54 // This ought to be just "allocate", because of the lock above, but that
55 // ContiguousSpace::allocate asserts that either the allocating thread
56 // holds the heap lock or it is the VM thread and we're at a safepoint.
57 // The best I (dld) could figure was to put a field in ContiguousSpace
58 // meaning "locking at safepoint taken care of", and set/reset that
59 // here. But this will do for now, especially in light of the comment
60 // above. Perhaps in the future some lock-free manner of keeping the
61 // coordination.
62 HeapWord* res = ContiguousSpace::par_allocate(size);
63 if (res != NULL) {
64 _offsets.alloc_block(res, size);
65 }
66 return res;
67 }
68
69 inline HeapWord*
70 OffsetTableContigSpace::block_start_const(const void* p) const {
71 return _offsets.block_start(p);
72 }
73
74 template <class SpaceType>
75 inline void CompactibleSpace::scan_and_forward(SpaceType* space, CompactPoint* cp) {
76 // Compute the new addresses for the live objects and store it in the mark
77 // Used by universe::mark_sweep_phase2()
78 HeapWord* compact_top; // This is where we are currently compacting to.
79
80 // We're sure to be here before any objects are compacted into this
81 // space, so this is a good time to initialize this:
82 space->set_compaction_top(space->bottom());
83
84 if (cp->space == NULL) {
85 assert(cp->gen != NULL, "need a generation");
86 assert(cp->threshold == NULL, "just checking");
87 assert(cp->gen->first_compaction_space() == space, "just checking");
88 cp->space = cp->gen->first_compaction_space();
89 compact_top = cp->space->bottom();
90 cp->space->set_compaction_top(compact_top);
91 cp->threshold = cp->space->initialize_threshold();
92 } else {
93 compact_top = cp->space->compaction_top();
94 }
95
96 // We allow some amount of garbage towards the bottom of the space, so
97 // we don't start compacting before there is a significant gain to be made.
98 // Occasionally, we want to ensure a full compaction, which is determined
99 // by the MarkSweepAlwaysCompactCount parameter.
100 uint invocations = MarkSweep::total_invocations();
101 bool skip_dead = ((invocations % MarkSweepAlwaysCompactCount) != 0);
102
103 size_t allowed_deadspace = 0;
104 if (skip_dead) {
105 const size_t ratio = space->allowed_dead_ratio();
106 allowed_deadspace = (space->capacity() * ratio / 100) / HeapWordSize;
107 }
108
109 HeapWord* q = space->bottom();
110 HeapWord* t = space->scan_limit();
111
112 HeapWord* end_of_live= q; // One byte beyond the last byte of the last
113 // live object.
114 HeapWord* first_dead = space->end(); // The first dead object.
115 LiveRange* liveRange = NULL; // The current live range, recorded in the
116 // first header of preceding free area.
117 space->_first_dead = first_dead;
118
119 const intx interval = PrefetchScanIntervalInBytes;
120
121 while (q < t) {
122 assert(!space->scanned_block_is_obj(q) ||
123 oop(q)->mark()->is_marked() || oop(q)->mark()->is_unlocked() ||
124 oop(q)->mark()->has_bias_pattern(),
125 "these are the only valid states during a mark sweep");
126 if (space->scanned_block_is_obj(q) && oop(q)->is_gc_marked()) {
127 // prefetch beyond q
128 Prefetch::write(q, interval);
129 size_t size = space->scanned_block_size(q);
130 compact_top = cp->space->forward(oop(q), size, cp, compact_top);
131 q += size;
132 end_of_live = q;
133 } else {
134 // run over all the contiguous dead objects
135 HeapWord* end = q;
136 do {
137 // prefetch beyond end
138 Prefetch::write(end, interval);
139 end += space->scanned_block_size(end);
140 } while (end < t && (!space->scanned_block_is_obj(end) || !oop(end)->is_gc_marked()));
141
142 // see if we might want to pretend this object is alive so that
143 // we don't have to compact quite as often.
144 if (allowed_deadspace > 0 && q == compact_top) {
145 size_t sz = pointer_delta(end, q);
146 if (space->insert_deadspace(allowed_deadspace, q, sz)) {
147 compact_top = cp->space->forward(oop(q), sz, cp, compact_top);
148 q = end;
149 end_of_live = end;
150 continue;
151 }
152 }
153
154 // otherwise, it really is a free region.
155
156 // for the previous LiveRange, record the end of the live objects.
157 if (liveRange) {
158 liveRange->set_end(q);
159 }
160
161 // record the current LiveRange object.
162 // liveRange->start() is overlaid on the mark word.
163 liveRange = (LiveRange*)q;
164 liveRange->set_start(end);
165 liveRange->set_end(end);
166
167 // see if this is the first dead region.
168 if (q < first_dead) {
169 first_dead = q;
170 }
171
172 // move on to the next object
173 q = end;
174 }
175 }
176
177 assert(q == t, "just checking");
178 if (liveRange != NULL) {
179 liveRange->set_end(q);
180 }
181 space->_end_of_live = end_of_live;
182 if (end_of_live < first_dead) {
183 first_dead = end_of_live;
184 }
185 space->_first_dead = first_dead;
186
187 // save the compaction_top of the compaction space.
188 cp->space->set_compaction_top(compact_top);
189 }
190
191 template <class SpaceType>
192 inline void CompactibleSpace::scan_and_adjust_pointers(SpaceType* space) {
193 // adjust all the interior pointers to point at the new locations of objects
194 // Used by MarkSweep::mark_sweep_phase3()
195
196 HeapWord* q = space->bottom();
197 HeapWord* t = space->_end_of_live; // Established by "prepare_for_compaction".
198
199 assert(space->_first_dead <= space->_end_of_live, "Stands to reason, no?");
200
201 if (q < t && space->_first_dead > q && !oop(q)->is_gc_marked()) {
202 // we have a chunk of the space which hasn't moved and we've
203 // reinitialized the mark word during the previous pass, so we can't
204 // use is_gc_marked for the traversal.
205 HeapWord* end = space->_first_dead;
206
207 while (q < end) {
208 // I originally tried to conjoin "block_start(q) == q" to the
209 // assertion below, but that doesn't work, because you can't
210 // accurately traverse previous objects to get to the current one
211 // after their pointers have been
212 // updated, until the actual compaction is done. dld, 4/00
213 assert(space->block_is_obj(q), "should be at block boundaries, and should be looking at objs");
214
215 // point all the oops to the new location
216 size_t size = oop(q)->adjust_pointers();
217 size = space->adjust_obj_size(size);
218
219 q += size;
220 }
221
222 if (space->_first_dead == t) {
223 q = t;
224 } else {
225 // $$$ This is funky. Using this to read the previously written
226 // LiveRange. See also use below.
227 q = (HeapWord*)oop(space->_first_dead)->mark()->decode_pointer();
228 }
229 }
230
231 const intx interval = PrefetchScanIntervalInBytes;
232
233 debug_only(HeapWord* prev_q = NULL);
234 while (q < t) {
235 // prefetch beyond q
236 Prefetch::write(q, interval);
237 if (oop(q)->is_gc_marked()) {
238 // q is alive
239 // point all the oops to the new location
240 size_t size = oop(q)->adjust_pointers();
241 size = space->adjust_obj_size(size);
242 debug_only(prev_q = q);
243 q += size;
244 } else {
245 // q is not a live object, so its mark should point at the next
246 // live object
247 debug_only(prev_q = q);
248 q = (HeapWord*) oop(q)->mark()->decode_pointer();
249 assert(q > prev_q, "we should be moving forward through memory");
250 }
251 }
252
253 assert(q == t, "just checking");
254 }
255
256 template <class SpaceType>
257 inline void CompactibleSpace::scan_and_compact(SpaceType* space) {
258 // Copy all live objects to their new location
259 // Used by MarkSweep::mark_sweep_phase4()
260
261 HeapWord* q = space->bottom();
262 HeapWord* const t = space->_end_of_live;
263 debug_only(HeapWord* prev_q = NULL);
264
265 if (q < t && space->_first_dead > q && !oop(q)->is_gc_marked()) {
266 #ifdef ASSERT // Debug only
267 // we have a chunk of the space which hasn't moved and we've reinitialized
268 // the mark word during the previous pass, so we can't use is_gc_marked for
269 // the traversal.
270 HeapWord* const end = space->_first_dead;
271
272 while (q < end) {
273 size_t size = space->obj_size(q);
274 assert(!oop(q)->is_gc_marked(), "should be unmarked (special dense prefix handling)");
275 prev_q = q;
276 q += size;
277 }
278 #endif
279
280 if (space->_first_dead == t) {
281 q = t;
282 } else {
283 // $$$ Funky
284 q = (HeapWord*) oop(space->_first_dead)->mark()->decode_pointer();
285 }
286 }
287
288 const intx scan_interval = PrefetchScanIntervalInBytes;
289 const intx copy_interval = PrefetchCopyIntervalInBytes;
290 while (q < t) {
291 if (!oop(q)->is_gc_marked()) {
292 // mark is pointer to next marked oop
293 debug_only(prev_q = q);
294 q = (HeapWord*) oop(q)->mark()->decode_pointer();
295 assert(q > prev_q, "we should be moving forward through memory");
296 } else {
297 // prefetch beyond q
298 Prefetch::read(q, scan_interval);
299
300 // size and destination
301 size_t size = space->obj_size(q);
302 HeapWord* compaction_top = (HeapWord*)oop(q)->forwardee();
303
304 // prefetch beyond compaction_top
305 Prefetch::write(compaction_top, copy_interval);
306
307 // copy object and reinit its mark
308 assert(q != compaction_top, "everything in this pass should be moving");
309 Copy::aligned_conjoint_words(q, compaction_top, size);
310 oop(compaction_top)->init_mark();
311 assert(oop(compaction_top)->klass() != NULL, "should have a class");
312
313 debug_only(prev_q = q);
314 q += size;
315 }
316 }
317
318 // Let's remember if we were empty before we did the compaction.
319 bool was_empty = space->used_region().is_empty();
320 // Reset space after compaction is complete
321 space->reset_after_compaction();
322 // We do this clear, below, since it has overloaded meanings for some
323 // space subtypes. For example, OffsetTableContigSpace's that were
324 // compacted into will have had their offset table thresholds updated
325 // continuously, but those that weren't need to have their thresholds
326 // re-initialized. Also mangles unused area for debugging.
327 if (space->used_region().is_empty()) {
328 if (!was_empty) space->clear(SpaceDecorator::Mangle);
329 } else {
330 if (ZapUnusedHeapArea) space->mangle_unused_area();
331 }
332 }
333 #endif // SHARE_VM_MEMORY_SPACE_INLINE_HPP